Modern communication systems demand multiband antenna performance. An apparatus to address this need is by using reconfigurable antennas. Reconfigurable antennas are known. However, an increasing demand for reconfigurable systems, which are also versatile, has not yet been satisfactorily addressed. In particular, there is a need to provide a reconfigurable antenna operable at multiple frequencies. At the present time, multiple frequencies are obtained by utilizing PIN diodes or many different antennas in order to have an antenna for each desired frequency. Another approach has been to reconfigure antennas, particularly the reconfigurable aperture (recap) antenna with micro-electromechanical (MEMS) switches, which has been unsuccessful, and microstrip antennas using PIN diodes, with some success. Still another approach includes the use of known “Sierpinski” type multiband antennas. However, the known Sierpinski type antennas only radiate at a number of frequencies, related to the number of iterations of the Sierpinski structure. Accordingly, even with these reconfigurable antennas, there is no provision for an antenna including on-demand selection of one of three predetermined frequencies.
An integration of RF-MEMS switches into known antenna systems has been attempted; however, an integration of RF-MEMS switches with the antenna has not been satisfactorily achieved. Moreover, no multiband antenna has been shown or reported to be RF-MEMS reconfigurable. In particular, there continue to be problems overcoming the effect of switch bias lines on the antenna performance. The bias lines of the RF-MEMS switches have been found to problematically affect the radiation pattern of the antenna, as well as its resonant frequencies.
Furthermore, recovery from these problems can be difficult. For example, the continued miniaturization of antennas and their parts prevents spacing of bias lines at intervals which will not interfere with the radiation patterns of the antenna. One reason for the desired use of MEMS switches resides in their lower insertion loss, lower power requirements, higher linearity, reliability, and better isolation effects than any other biasing method such as, for example, PIN/FET. However, incorporation of these switches into an antenna configuration has not previously been successful because of the inability to bias them and place them in a way to not affect antenna performance. Disadvantages include their long switching times (on the order of 1-20 μs), high actuation voltage and they are unable to handle high-power RF applications.
Thus, there is a need to overcome these and other problems of the prior art and to provide a reconfigurable multifrequency antenna with RF-MEMS switches. The present invention successfully integrates RF-MEMS switches with compatible antenna structures in a very efficient way that enhances the performance of the conventional antenna by adding an additional resonant frequency without altering its radiation pattern.